Propeller containing diagonally disposed fibrous material



Oct. ll, 1949. 2,484,308

M. M. MUN PROPELLER CONTAINING DIAGONALLY DISPOSED FIBROUS MATERIAL Filed Aug. 25, 1947 Patented Oct. 11, 1949 UNITED STATES PATENT GFFICE PROPELLER CONTAINING DIAGONALLY DISPOSED FIBROUS MATERIAL 3 Claims.

This invention relates to aerial propellers having fixed pitch blades, said blades containing at least in part brous material such as. wood distinguished by greater stiiness in the direction of the fibres than in direction at right angles to the bres.

Ordinary fixed pitch propellers tend to increase their pitch elastically as the thrust increases, or at least they do not diminish their pitch as the thrust increases. The contrary elastic behaviour, namely a tendency to diminish the `pitch angle elastically as the thrust increases is desirable for reason of performance, and relatively small favorable elastic twist angles noticeably improve the performance of the propellers. This is well understood from the action and operation of variable pitch propellers.

It is the purpose l,of the present invention to provide a fixed :pitch propeller the blades of which twist elasttcally and favorably as the thrust changes.

This is accomplished by making at least a portion of the blade of fibrous material, preferably wood, so disposed that the bres are disposed diagonally and not radially.

This will plow be illustrated in the accompanying drawing and described in the specification, a certain preferred embodiment being disclosed by way of illustration only, for, since the underlying lprinciple may be incorporated in other propellers it is not intended to be limited to the propeller shown except as such limitations are clearly imposed by the appended claims.

In the drawing like numerals refer to similar parts throughout the several views, of which Fig. 1 represents the rear or pressure side fractional View of a right hand turning wood propeller incorporating the invention.

Fig. 2 represents the same Ipropeller in the same manner in front View or suction side View.

Fig. 3 represents the cross section through the same pnopeller taken on line `3--3 in Fig. 2.

In Figs. l and 2 only one blade is shown, the other blade is supposed to be cut o as not showing anything new. The propeller has in all two blades denoted broadly by I I, extending radially from hub Iii to tip i2. The hub II) is considered inward the tip I2 is considered outward The blades have a leading edge I3 and a trailing edge I4. They notate from lil to I3, which direction of motion is designated as forwardly In Figs. l and 2 the usual tip guards of brass or other material are omitted so as not to obscure the View, but it is contemplated to provide the propeller with the usual tip guards.

The intermediate or inner main portion of the blade, I5, is glued up of wood with the wood fibres extending substantially radially, as is cornmon practice.

Two outer auxiliary blade portions, front portion I6 and rear portion Il, also sof wood, are glued to the inner portion I5. The wood bres of portions IE and Il are diagonally disposed, in that they form asubstantial angle with the radial direction, preferably about 45 degrees. The bres of I6 and of Il extend outwardly and forwardly as these terms `were before dened. The bre direction of the several blade portions is indicated in Figs. l and 2. Note that the fibres of the auxiliary layers I6 and Il run substantially parallel.

The relative disposition of blade portions I5, I6, and I'l is clearly shown in the cross section Fig. 3. In Fig. 3, upwardly and rightwardly hatching indicates a substantially radial nbre direction, and downwardly and rightwardly hatching indicates a diagonal bre direction, all substantially the same diagonal direction, namely outwardly and forwardly as explained and drawn in Figs. 1 and 2.

All blade Iportions mentioned are securely glued together. The glue surfaces I8 in Fig. 3 appear as straight lines in this peripheral cross section. This is preferred for ease of manufacture.

The peculiar elastic twisting effect obtained is caused entirely by the specified diagonal direction of the fibres, and not by the combination of diagonal bres with radial bres. This combination is preferred by =Way of a compromise, for the purpose of obtaining the twisting effect without impairing the strength excessively. The reality of the twisting effect is beyond doubt, it can easily be observed on small wood samples having its fibres diagonally disposed. The actual twisting obtained in the propeller blade is quite small, but even a fraction of a degree brings about noticeable improvements of the performance.

I claim:

1. In an aerial propeller a solid laminated radial wooden blade lconsisting of a main portion in which substantially all wood iibres are radially disposed, and of one or more auxiliary layers in which substantially all wood fibres are diagonally disposed, all said diagonally disposed iibres eX- tending in forward and outward direction, the auxiliary layers being glued to the main portion to form a solid blade, whereby the blade will 3 elastically decrease its pitch angle with increasing thrust.

2. In a xed pitch aerial propeller a solid laminated radial Wooden blade consisting of an inner portion in which substantially all the wood fibres are radially disposed, and of an upper and a lower portion in which substantially all of the wood fibres.. are. diagonally disposed, the upper and the lower portions being glued to the innerv all of the wood fibres of the upper and of the,-

lower portions extending forwardly and outwardly.

3. In a fixed pitch aerial pnopelleralsoldlarni-A nated radial Wooden blade consisting; of. a main; portion in which all wood fibres are radially dislposed, and of one or more auxiliaryf layer-s1 in1 which all wood fibres are diagonally disposed, all said diagonally disposed fibres extending in forward and outward direction, the auxiliary layers being glued to the main portion tov form a.r

,main portion and the auxiliary layers being curved so as to contain a continuous succession :of straight lines at right angle to the blade and a continuous succession of at least partially curved lines lengthwise of the blade, their curvature being concave in relation to the main p0rtion.

MAX M. MUNK.

REFERENCES CITED- The following references are of record in the file of this patent:

STATES PATENTS Number Name Date l,4l79.94f Lochman Mar. 13, 1923 1,875,597 Heath Sept. 6, 1932 1,967g735 Bendix' July 24, 1934 2,273,259A Gischow Mar` 3l, 1942 FOREIGN?V PATENTS Number Country Date.

379,284 Great' Britain Aug. 23, 1932. 5,114,311 France June 30J V1920 

